Nonwoven fabrics are composed of fibers which may be consolidated by purely mechanical means such as, for example, by entanglement caused by needle-punching, by an air-laid process, and by a wet-laid process; by chemical means such as, for example, treatment with a polymeric binder; or by a combination of mechanical and chemical means before, during, or after nonwoven fabric formation. Some nonwoven fabrics are used at temperatures substantially higher than ambient temperature such as, for example, glass fiber-containing nonwoven fabrics which are impregnated with a hot asphaltic composition pursuant to making roofing shingles or roll roofing material. When a nonwoven fabric is contacted with a hot asphaltic composition at temperatures of 150-250.degree. C., the nonwoven fabric may sag, shrink, or otherwise become distorted. Therefore, nonwoven fabrics which incorporate a curable aqueous composition should substantially retain the properties contributed by the cured aqueous composition such as, for example, tensile strength. In addition, the cured composition should not substantially detract from essential nonwoven fabric characteristics, as would be the case, for example, if the cured composition were too rigid or brittle or became sticky under processing conditions.
There is a need for a method for making a heat-resistant nonwoven fabric by using heat-resistant fibers and a heat-resistant curable aqueous composition which is free of formaldehyde, because of existing and proposed legislation directed to the lowering or elimination of formaldehyde